Facebook friend, or Facebook as a foe? The social media revolution is proving a double-edged sword in schools.

On the one hand, it provides teachers with a new educational tool that students love.

A good example recently cited to the Irish Independent involved giving students an exercise involving Twitter when they where studying the novel 'To Kill a Mocking Bird'.

On the other hand, social media networks have put a powerful tool in the hands of all, one that can be used to cause lasting damage to reputations.

Ferdia Kelly, general secretary of the Joint Managerial Body, representing over 400 secondary schools, said there were lots of positives, but schools were dealing with increasing incidences of cyber-bullying, more usually between students.

Traditional forms of bullying, whether against other student or teachers, are no more acceptable -- but at least they may be more easily erased and contained.

Facebook has presented school communities with other challenges. Clive Byrne of the National Association of Principals and Deputy Principals said it was best practice for teachers not to have students as a Facebook "friend".

The Association of Secondary Teachers Ireland (ASTI) has advised members to check privacy settings on Facebook so that they know who can access their information.

Under Facebook guidelines, users must be at least 13 to set up an account, but children sometimes lie about their age.

Earlier this week, a school principal in Australia warned that pupils under 13 who did not delete their Facebook accounts would be expelled.